The use of radiation to treat medical conditions comprises a known area of prior art endeavor. For example, radiation therapy comprises an important component of many treatment plans for reducing or eliminating unwanted tumors. Unfortunately, applied radiation does not discriminate between unwanted structures and adjacent tissues, organs, or the like that are desired or even critical to continued survival of the patient. As a result, radiation is ordinarily applied in a carefully administered manner to at least attempt to restrict the radiation to a given target volume.
Collimators are often used to restrict and form the radiation-therapy beam. Many collimators have an aperture that can be adjusted in one or more dimensions. Adjustable apertures permit, to at least some degree, customization of the radiation-therapy beam's cross section to thereby attempt to better match the requirements of a given target volume. Multi-leaf collimators are an example of such a component. Multi-leaf collimators are comprised of a plurality of individual parts (known as “leaves”) that are formed of a high atomic-numbered material (such as tungsten) that can move independently in and out of the path of the radiation-therapy beam in order to selectively block (and hence shape) the beam.
Many treatment plans provide for exposing the target volume to radiation from a number of different directions. Arc therapy, for example, comprises one such approach. In such a case it often becomes useful or necessary to adjust the multi-leaf collimator to accommodate various differences that occur or accrue when moving the radiation source with respect to the target volume. A radiation-treatment plan therefore often provides information regarding useful or necessary adjustments to the multi-leaf collimator(s) during such a treatment.
Such plans are often calculated using an iterative process. Beginning with some initial set of settings, a radiation-treatment planning apparatus iteratively adjusts one or more of those settings and assesses the relative worth of the adjusted plan. An iterative approach such as this is often referred to as “optimizing” the plan (where “optimizing” should not be confused with the idea of identifying an objectively “optimum” plan that is superior to all other possible plans).
Optimizing such a plan can prove challenging as the overall computational requirements can be considerable. As one example in these regards, such a candidate treatment plan often comprises a plurality of control points (pertaining, for example, to collimator leaf settings at each of a plurality of source angles in an arc therapy application setting).
The radiation-treatment platform that will serve to administer the radiation in accordance with the optimized plan has corresponding physical limitations. For example, the source will typically move no faster than some given speed during the treatment and the multi-leaf collimator used during that treatment can only change its aperture settings subject to some maximum speed. A treatment plan that fails to account for such physical characteristics can ultimately be unusable if the aperture settings from one position to the next are physically impossible to achieve.
In some application settings, the time required to work through such iterative calculations can result in vexing delays. These delays, in turn, can lead to expensive and undesirable equipment downtime, patient discomfort, and increased costs.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.